Incorporating oil in hardboard



an m United States PatentQ 2,978,382 INCORPORATING OIL IN HARDBOARD Historically, oil tempered boards have been manufach I tuned by dipping the finished hardboard in a large tank of drying oil leaving the hardboard for a short interval of time in the oil to permit absorption and thereafter baking the oil soaked board in an oven at a temperature within the range of 300400 F. for 3-6 hours in order to set the oil to a resin-like material. This conventional manner of manufacturing requires a monetary outlay for .the installation and maintenance of oildipping equipment and frequently the tempering oil is not uniformly distributed throughout the board as there is a greater .saturation of the board at the two surfaces than in the interior. Boards are tempered primarily to increase strength and in addition, the oil will impart some resista nce to weather.

' We have found that drying oil may be readily incorporated in a hardboard with apparently more uniformity of dispersion, with less equipment, with a saving in time .overthat required in conventional manufacture and with less oil required to accomplish the end result. process of our invention, we propose to incorporate the drying oil into the fibrous hardboard by dispersing in a water slurry of the fibrous material a finely divided dry fat sorbing material which carries an appreciable amount of the drying oil. The water of the slurry is drawn off leaving a mat of the fibrous material and the oil soaked fat-retaining material on a felting screen. The fibrous mat is subsequently subjected to a conventional hot pressing operation to extract the remaining moisture and to assist in the distribution of the drying oil throughout the mat using the echnique of dry rendering under the pressure and temperature conditions maintained between .the press platens. Following hot pressing, the boardis then subjected to a conventional baking operation to set the drying oil to a resin-like material.

In the 2,978,382 il atented Apr. fl,

Certain earths and clays, for example, china clay, fullers earth, diatomaceous earth and various alumino silicate earths are capable of retaining large amounts of oil. It has been our experience that if these earths are finely powdered, they may carry large quantities ofdrying 'oil, without losing their powdered state. The oil soaked earths when introduced to and agitated in a fibrous slurry of the type conventionally prepared in hardboard manufacture will tend to remain dispersed throughout the body 'of the slurry and neither float nor sink. We prefer to incorporate the oil in an amount of 10-30% based on .the weight of the dry earth. Amounts much in excess of 30% result in leaching out of the oil. When the'slurry is felted to remove most of the water and to form amat, the oil soaked earth will be substantially uniformly dispersed throughout the wet mat. In the subsequent hot pressing operation, the oil will be retained by the earth until the moisture has escaped the board. After the extraction of the water, the oil renders from the earth and distributes itself substantially uniformly throughout the cellulosic fibrous mat. 'If the tempering oils should be added directly to the water slurry without the vehicle of an adsorbing earth, a portion of the oil will form an emulsion with the water and 'when the free water is pressed out of the fibrous mat,

there will be a considerable loss of the oil in the extracted oil-water emulsion. It has also been noticed that the presence of oil-water emulsions in the felted mat tends to inhibit the freeness of the fiber as measured by felting ratesr In addition" to this novel and expedient method for introducing and dispersing tempering oils in a hardboard composition, the practice of our process has other advantages. It provides an inexpensive filler for the small 'voids and increases the density of the board without decreasing its strength. The hardboard manufactured in accordance with the process of the instant process is especially suitable, among other purposes, for shelving,

, may be utilized include finely ground wood (wood flour),

A diagrammatic representation of the process is as follow:

LForm Water slurry of fibrous material V l Precipitate binder on material 7 I Suspended in water slurry fat retaining material containing drying oil Felt fibrous material and fatretaining material on screen Hot press I Polymerize drying oil I powdered linters, walnut shell flour, and pulverized cottonseed hulls. All of these materials should be dry and powdered orfinely divided. Linters are the fibers removed from cottonseeds prior to extracting or expelling the oil. It has been our experience that powdered material having a mesh within the range of 50 to 300 is of a size which, when oil soaked, may be readily dispersed in the water slurry and less likely to either float or settle. If the powdered material is fibrous, then coarser grades may be used. The drying oil is preferably mixed with the dry powder in an amount within the range of 1030% based on theweight of the dry material. g,

Spent fullers earth from. the bleaching operation of the glyceride oil industry is an excellent source material.

'This material which normally has little value will con tain usually on the order of 20% free 'oil adsorbed thereon and absorbed therein. The spent earth should be finely powdered.

The oil soaked fat sorbing material may be prepared in The material, whether it' be is then finely divided to a powdered state, preferably to ,a mesh size with the range of 50 to 300-if earthenih origin. It will not be possible to subdivide the cellulosic .materials to the extent that may be done in theinstance of the earths. The finely divided material is then placed ,rna rmxer and theoil added with continuous agitation,

The material l Excessive quantities of the oil should not be used; otherwise, the material will mud" which should be avoided as the material should remain finely divided in a powder form in order to be uniformly dispersed throughout'the water slurry.

Any of the drying oils commercially used in'the manufacture of tempered hardboards may be utilized in our process. octicica, dehydrated castor audthe like. We have found that it is sometimes advantageous when using spent fullcrs earth from cottonseed oil bleaching to add a small amount of tung oil. Tung oil is more unsaturated than cottonseed oil and the inclusion of a small amount of it will increase the strength of the board.

It is preferred that the oil soaked earth or other fatretaining material be introduced to the water slurry after the binder has been precipitated upon the fibers; otherwise, the oil soaked materials will inhibit to some extent the adhesion of the binder to the fibrous material.

The amount of the oil soaked fat-retaining material that is incorporated in the fibrous slurry may be varied considerably, depending principally upon the characteristics that are desired in the finished hardboard. The greater the amount of oil soaked earth or other fatretaining material that is present in the hardboard, the less the flexibility and the greater the density. From our experience, hardboard containing -20% of the fatretaining material based on the dry weight of the fibrous material results in a hardboard especially suitable for use as an underlayment for fioorings. Boards containing this proportion of fat-retaining material may also be used for shelving and drawer bottoms.

The following examples are set forth as illustrative of the present invention and are not to be construed as limiting thereto.

Example I The paunch contents (rumen) of slaughtered cattle were utilized as the fibrous material in the manufacture of the hardboards of this example. The rumen was first beaten and then subjected to flotation whereby the fibers were floated and undesirable constituents were settled out. The rumen fibers were then passed through a Bauer mill, set to a clearance of .025". The milled fibers were then concentrated for further use by separation of the solids over a screen. The screened material at this point had a solids content of approximately 20%, with the rest being Water. The slurry was diluted with water to obtain a solids content of 4% and then divided into 4 equal portions. The first portion was transferred to a batch type felting postion wherein the free water was drained off to form a mat of felted fibers. To the slurry of the second portion, a phenolic formaldehyde water soluble resin was added. The resin was precipitated upon the fibrous material and the slurry felted to form a mat. The other two portions of the slurry received this same binder which in each instance was first precipitated upon the fibers of the slurry before the introduction of a fat-retaining material to the respective slurries. In the instance of the third portion, spent fullers earth from cottonseed oil refining was added in an amount of 10% of the weight of the dry fibrous material. The fourth board likewise contained fullers earth but here the fullers earth had had added to it tung oil in the amount of 30% of the weight of the earth.

Each of the four mats were then subjected to a cold pressing operation to remove the major portion of water retained in the material. Each mat was then placed in a conventional hot plate press maintained at a temperature of 385 F. andpressed for five minutes under 200 p.s.i. All of the boards were then transferred to an oven having a temperature of 350 F. for five hours.

The following table contains data pertinent to the modulus of rupture, to percent weight increase, and to the percent thicknessincrease of-the boards afterimmersion Among these are soya, tung, linseed, safflower,

for 24 hours in water. The modulus of rupture data was collected on dry boards.

having a mesh size of approximately '100-200and contained approximately 20% of cottonseed oil based on the Weight of the earth. The fullers earth which carried the tung oil likewise was finely powdered having a mesh size of about -200 and had been prepared in the manner described above.

Example II The fibrous stock used to make the hardboard of this example was aspen wood which was prepared in the manner described above except that the Bauer mill was set to a clearance of .040. Here again, the binder used was a water soluble phenol formaldehyde resin which was added to the fibrous slurry in the amount of 2% based on the weight of the dry fiber and precipitated therefrom before the addition of the finely divided oil soaked material. After precipitation of the resin onto the fibrous material of the slurry, the slurry was subdivided into two equal portions. To one of these portions, walnut shell flour which carried 30% of its own weight of tung oil was introduced with agitation. The oil soaked walnut shell flour constituted 10% of the solid contents of the finished hardboard. The subsequent proc-- essing of the two portions of the slurry was substantially in the manner described in Example I except that the baking operation was at 400 F. for 3 hours. The following table sets forth the pertinent information relating to the two hardboards:

Thickness Moi ture Expansion M.R. Absorption, Due to percent Moisture,

percent Aspen Fiber Board 2, 100 55 60 Aspen Board treated with 3% Tung Oil on 10% Walnut Shell Flour... 4, 120 22 11 Example III The hardboard specimens of this example were pre pared in a like manner to that of Example I and here, finely divided wood (fir) flour with a mesh of 50 or less was utilized to carry soya oil. The oil soaked wood flour was incorporated in the fibrous slurry in an amount of 15% of the dry weight of the fibrous material. The soya oil made up 20% of the weight of the oil soaked wood flour. The fibrous stock was aspen wood. Water soluble phenol formaldehyde resin was employed as the binder and again it was precipitated from the water of the slurry onto the aspen fiber before introduction of the oil soaked wood flour. The control which contained Wood flour had a modulus of rupture of 2200 p.s.i. and a moisture percent'weight increase after immersion in water for 24 hours of 53%. The thickness increase due to absorption of water-was 58%. The oil tempered board had an appreciably greater modulus of rupture of 4050 p.s.i., a percent weight increase of 20% and a percent thickness increase of The soya drying oil was added to the wood flour in a manner described above to obtain a free flowing powder which was readily dispersed in the slurry.

Example IV China clay carrying of its weight of linseed oil was utilized in this example. The oil soaked earth was prepared in the manner described above and was incorporated with agitation into an aqueous slurry of fir fibers in an amount of of the dry weight of the fibers. The board was prepared in a manner substantially like that of Example I with phenol formaldehyde resin being used as a binder which binder was precipitated from the Water of the fibrous slurry before addition of the oil soaked earth. The control board had a modulus of rupture of 4600 p.s.i., a percent weight increase of 48%, and a percent thickness increase of 40%. The latter two values were obtained after immersion of the board in water for 24 hours. The test board which contained the china clay uniformly dispersed throughout had a modulus of rupture of 5800 p.s.i., a moisture absorption percent increase of 18%, and a percent thickness increase of 9%.

Example V The work of this example was with diatomaceous earth and safiiower oil. The process was substantially like that described in Example I with the oil soaked diatomaceous earth making up 25% of the dry weight of the hardboard. Aspen wood was used for the fibrous stock. The safliower oil constituted 25% of the weight of the oil soaked diatomaceous earth. The control had a modulus of rupture of 3000 p.s.i., a moisture absorption percent increase of 62%, and a percent thickness increase of 51%. The treated board tested 4800 p.s.i., 22% and 14% respectively.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of manufacturing an oil tempered fibrous hardboard comprising: forming a water slurry of fibrous sion suspension by suspending in the water slurry a finely divided fat-retaining material containing a substantial amount of a drying oil, felting the fibrous material and the,

oil soaked fat-retaining material onto a screen to form a fibrous mat, hot pressing the fibrous mat to substantially remove the excess water and to distribute the drying oil 7 throughout said mat, and subsequently heating the mat at an elevated temperature for a period of time suflicient to polymerize the drying oil.

2. A process as described in claim 1 wherein the retaining material is fullers earth.

3. A process in accordance with claim 1 wherein the retaining material is spent fullers earth from a glyceride oil refining.

4. A process in accordance with claim 1 wherein the retaining material is walnut shell flour.

5. A process in accordance with claim 1 wherein the drying oil is tung oil.

6. A process in accordance with claim 1 wherein the drying oil is linseed oil.

7. The process as described in claim 1 wherein the drying oil constitutes 10-30% of the Weight of the fatretaining material.

8. The process as described in claim 1 wherein the oil soaked fat-retaining material constitutes from 10- 20% of the dry weight of the fibrous material.

References Cited in the file of this patent UNITED STATES PATENTS 940,969 Hinkel Nov. 23, 1909 1,000,598 Hall Aug. 15, 1911 1,401,791 Kirschbraun Dec. 27, 1921 1,499,291 Castner June 24, 1924 1,753,690 Brown Apr. 8, 1930 1,786,270 Spencer Dec. 23, 1930 1,803,816 Strobel May 5, 1931 1,998,190 Finder et a]. Apr. 16, 1935 2,044,213 Irvine June 16, 1936 2,077,015 Schacht Apr. 13, 1937 2,143,831 Ellis et al. June 10, 1939 2,215,244 Linzell Sept. 17, 1940 2,703,293 Boehm et al. Mar. 1, 1955 2,721,504 Mossberg et al. Oct. 5, 1955 2,744,013 Dorland et al. May 1, 1956 

1. A METHOD OF MAUFACTURING AN OIL TEMPERED FIBROUS HARDBOARD COMPRISING: FORMING A WATER SLURRY OF FIBROUS MATERIAL WITH A BINDER DISPERSED THROUGHOUT, PRECIPITATING TTHE BINDER ONTOS THE FISBROUS MATERIAL, FORMING A NONEMULSION SUSPENSION BY SUSPENDING IN THE WATER SLURRY A FINELY DIVIDED FAT-RETAINING MATERIAL CONTAINING A SUBSTANTIAL AMOUNT OF A DRYING OIL, FELTING THE FIBROUS MATERIAL AND THE OIL SOAKED FAT-RETAINING MATERIAL ONTO A SCREEN TO FORM A FIBROUS MAT, HOT PRESSING THE FIBROUS MAT TO SUBSTANTIALLY REMOVE THE EXCESS WATER AND TO DISTRIBUTE THE DRYING OIL THROUGHOUT SAID MAT, AND SUBSEQUENTLY HEATING THE MAT AT AN ELEVATED TEMPERATURE FOR A PERIOD OF TIME SUFFICIENT TO POLYMERIZE THE DRYING OIL. 